In the previous post I suggested that the Venus flytrap works something like a mousetrap. And I described how the “trap” is hydraulically set. (For a more thorough explanation of how the Venus flytrap snaps, please see this PDF file).
But how do the trigger-hairs on the surface of the flytrap’s leaves act to “spring the trap”?
This action potential travels to the midrib of the leaf where it promotes the opening of water channels called aquaporins. This facilitates the rapid water efflux from key cells that hydraulically control the leaf opening.
More simply put, the stimulation of the leaf hairs produce electrical signals that cause the rapid deflation of the water-pressurized cells that keep the leaves open. And, thus, the “trap is sprung”.
Do plants have a nervous system?
The short answer is: no. (At least not the complex nervous system of animals.)
But scientists have been able to detect transient electrical signals somewhat analogous to action potentials under certain situations in plants.
Sparked by a correspondence with Darwin, which included some Venus flytrap plants, the English physiologist John Scott Burdon-Sanderson was the first to discover action potentials in plants following stimulation of a leaf. (Please see reference 1 below.)
In addition to thigmosnastic plants, all vascular plants may be utilizing electrical signals to regulate a variety of physiological functions.
Many of the biochemical and cellular components of the neuromotoric system of animals has been found in plants. And this has led to the hypothesis that a simple neural network is present in plants, especially within phloem cells, which is responsible for the communication over long distances.
“The reason why plants have developed pathways for electrical signal transmission is most probably the necessity to respond rapidly to external stimuli, for example, environmental stress factors.” (from ref 2 below)
More regarding electrical communication in plants: Novel electrical signals in plants induced by wounding
The Emerging Field of Plant Neurobiology
This review (PDF) introduced, to the plant scientific community at least, the field of “Plant Neurobiology”. Although this proposal was not without controversy (PDF), the Society for Plant Neurobiology seems to be alive and well (Plant Neurobiology Website). (And if you happen to be in Kitakyushu, Japan, in May this year, you may be able to attend the 6th International Symposium on Plant Neurobiology).
Bottom line: Though plants don’t have a nervous system like animals, plants do have the necessary electrical, biochemical, and cellular components indicative of a neural network, albeit a relatively simple one.
1. Burdon-Sanderson J. (1873) Note on the electrical phenomena which accompany irritation of the leaf of Dionaea muscipula. Proceedings of the Royal Society of London 21, 495–496.
2. Fromm, J. & S. Lautner (2007) Electrical signals and their physiological significance in plants. Plant, Cell and Environment 30, 249-257. (Full Text)
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